BRAINS OF EUROPEAN AND AMERICAN RATS COMPARED 87 
shot used weighed 6.354 grams + 0.020, hence the observed 
weight in grams is transformed into volumes in cubic centimeters 
by dividing the weight of the shot by 6.354. In tables 12 and 13 
the data on the cranial capacity in cubic centimeters are presented 
for each one of the entries. 
Taking the entries in table 12, which refer to the wild Norways, 
we wish in the first instance to learn how the cranial capacities 
of the several European series are related to that of the Phila- 
~ 
9. 4CRANIAL CAPACITY OF 
NORWAY RATS 24 
Cc, 
23 
2.2 
2.1 — PHILADELPHIA 24 
xe RECORDS 
CHART 3. 
BODY WEIGHT gms. 
60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 
Chart 3, showing the cranial capacity in cubic centimeters for the four Norway 
series. The values for the Philadelphia series are represented by a curve com- 
puted from formula (1). The values for the European series are entered sep- 
arately. O = Paris series, 0 = London series, V = Vienna series. 
delphia series taken as a standard. To show this, the European 
data have been plotted by groups on chart 3, while the Phila- 
delphia records are represented by a continuous line showing the 
computed values. For the formula for this line, I am indebted 
to Dr. Hatai. 
The relation between the computed and the observed values in 
the Philadelphia series is close. Except for the second entry 
at 128.2 grams, which entry is a trifle high, the observed data for 
the cranial capacity of the Philadelphia Norways show an orderly 
